Secretly look to see if he admires things other than your looks. If he compliments you on who you are and qualities that aren't aesthetic, then he's very likely not using you. If he only cares about your looks, then he is. Also, if he is impatient about things like kissing or beyond (like foreplay or sex), and it seems like he wants to just get on with it and doesn't care if it's intimate, then the kissing/beyond is all he cares about.